Deleting cookie in IE6

Hi.
I need some help here please.
I am building a site that needs authorization.
In order to do that , I am issuing a cookie in the login page,
and on every page, I'm checking if the cookie exists.
The problem begins when the user chooses " log out"
(which supposed to delete the cookie from the user's machine and redirect to the login page).
It works great in Mozilla and in Konqueror, but IE6 refuses to discard the cookie (and therefore allows access to pages (when the user clicks "Back" button or writing the url ) , eventhough the user is 'logged out')

In all the pages (besides the login page). there is a check if the cookie exists.
After logout, the check in IE6 shows that the cookie still exists.
I'm assuming that it has to do with caching the cookie on IE6.
I tried using headers that suppose to surpress the caching of the pages as well as surpressing the Set-Cookie header caching.
I used the recommendations written in the RFC2109 but it still doesn't work.
( I can't verify that the cookie exists / not exists in IE6 because I can't find it in the Hard drive)

I would recommend setting another cookie indicating that the user had logged out.
You could also put a date in the original cookie and have your code not allow the user back until a certain time after that date. good luck